TITLE:   GCN CIRCULAR
NUMBER:  33668
SUBJECT: GRB 230421A: Fermi GBM Final Real-time Localization
DATE:    23/04/21 13:54:39 GMT
FROM:    William Cleveland at NASA-MSFC <william.cleveland@nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 09:42:46 UT on 21 Apr 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230421A (trigger 703762971.373066 / 230421405).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 44.5, Dec = 6.0 (J2000 degrees, equivalent to J2000 02h 58m, 6d 00'), with a statistical uncertainty of 5.5 degrees.

The angle from the Fermi LAT boresight is 99.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_skymap_all_bn230421405.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_healpix_all_bn230421405.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif